The invention relates to a terminal for a wireless network for a metropolitan area. More particularly, the invention relates to a terminal for a wireless network including an Ethernet switch.
Computers utilized in modern office environments are typically coupled to a local area network (LAN). The LAN allows users of the computers to share common resources, such as a common printer included in the network, and allows the users to share information files, such as by including one or more file servers in the network. In addition, the users are typically able to communicate information with each other through electronic messaging. A commonly utilized type of LAN is Ethernet. Currently, a variety of products which support Ethernet are commercially available from a variety of sources. Other types of LANs are also utilized, such as token ring, fiber distributed data interface (FDDI) or asynchronous transfer mode (ATM).
LANs are often connected to a wide area network (WAN) via a telephone modem. Thus, information is communicated over the WAN via a communication link provided by a telephone service provider. These telephone links, however, are generally designed to have a bandwidth that is sufficient for voice communication. As such, the rate at which information can be communicated over these telephone links is limited. As computers and computer applications become more sophisticated, however, they tend to generate and process increasingly large amounts of data to be communicated. For example, the communication of computer graphics generally requires a large amount of bandwidth relative to voice communication. Thus, the telephone link can become a data communication bottleneck.
Business organizations and their affiliates are often spread over several sites in a metropolitan or geographical area. For example, a business organization can have a headquarters, one or more branch offices, and various other facilities. For such business organizations, LANs located at the various sites will generally need to communicate information with each other. Wireless communication links for connecting local area networks are known. For example, U.S. Pat. No. 4,876,742, entitled xe2x80x9cApparatus and Method for Providing a Wireless Link Between Two Area Network Systems,xe2x80x9d and U.S. Pat. No. 5,436,902, entitled xe2x80x9cEthernet Extender,xe2x80x9d each disclose a wireless communication link for connecting LANs.
Availability is a measure of the average number of errors which occur in digitally transmitted data. An availability of 99.99 percent is commonly required for radio communications. For an availability of 99.99 percent, the average error rate for digitally communicated data must be maintained below 1xc3x9710xe2x88x926 errors per bit, 99.99 percent of the time. The integrity of a wireless communication link, however, is largely dependent upon transient environmental conditions, Such as precipitation. Environmental precipitation causes a severe attenuation of the transmitted signal. For example, to maintain an availability of 99.99 in the presence of environmental precipitation, the signal must be transmitted at a level that is 24 dB/km higher than otherwise. Therefore, to ensure an acceptable data error rate under all expected conditions, data is typically communicated over a wireless communication link at a relatively high power and at a relatively low rate. The amount of data required to be communicated over the wireless link, however, can vary widely over time and can vary independently of environmental conditions. In addition, wireless links, especially those operated at high power levels, can cause interference with other wireless links operating in the same geographical area. Thus, the wireless link can become a data communication bottleneck.
Therefore, a technique is needed for efficiently and cost effectively communicating data over a wireless link between Ethernet local area networks.
The invention is a method and apparatus for an Ethernet switch in a terminal for a wireless metropolitan area network. In accordance with an aspect of the present invention, a terminal for a wireless link in a metropolitan area network includes a broadcast device having: a network switch having a first port for receiving data packets from a computer network and a second port for forwarding the data packets; rate buffers coupled to the network switch for receiving the data packets from the second port; and a wireless transceiver coupled to the rate buffers for receiving the data packets from the rate buffers and for communicating the data packets over the wireless link. The data packets can be Fast Ethernet data packets and the network switch can include a 100 mega-bits-per-second port for receiving the Fast Ethernet packets. The terminal can include packet buffers coupled to the network switch wherein the network switch selectively stores the data packets in the packet buffers prior to storing the data packets in the rate buffers. The network switch can be a layer-two switch. The layer-two switch can store the data packets in the packet buffers in response to a level of space available in the rate buffers. The layer-two switch can store the data packets in the packet buffers in response to rain fade in the wireless link. The layer-two switch can store the data packets in the packet buffers in response to interference in the wireless link. The layer-two switch can store the data packets in the packet buffers in response to a detected bit error rate for communication via the wireless link. The terminal can include an extender device coupled to the broadcast device for receiving the data packets from the computer network and for providing the data packets to the broadcast device.
In accordance with another aspect of the present invention, a terminal for a wireless link in a metropolitan area network includes a broadcast device having: a network switch having a first port for receiving a first portion of data packets from a computer network, a second port for receiving a second portion of the data packets from the computer network and a third port for forwarding the data packets; rate buffers coupled to the network switch for receiving the data packets from the third port; and a wireless transceiver coupled to the rate buffers for receiving the data packets from the rate buffers and for communicating the data packets over the wireless link. The terminal can include packet buffers coupled to the network switch wherein the network switch selectively stores the first portion of data packets in the packet buffers prior to storing the first portion of data packets in the rate buffers. The network switch can store the second portion of the data packets in the rate buffers while the network switch stores the first portion of the data packets in the packet buffers. The first port can be a 100BASE-T port and the second port can be a 10BASE-T port. The network switch can be a layer-two switch.
In accordance with a further aspect of the present invention, a terminal for a wireless link in a metropolitan area network includes: an extender device for receiving data packets from a computer network coupled to the extender device and for forwarding the data packets; and a broadcast device coupled to the extender device and having a network switch for receiving the data packets from the extender device and a wireless transceiver coupled to the network switch for communicating the data packets over the wireless link. The terminal can include packet buffers coupled to the network switch wherein the network switch selectively stores the data packets in the packet buffers. The terminal can include rate buffers coupled to the network switch wherein the network switch stores the data packets in the rate buffers during periods when the network switch does not store data packets in the packet buffers. The terminal can include a packet formatting apparatus for formatting the data packets into radio frames wherein the packet formatting apparatus receives the data packets from the rate buffers. The data packets can be Fast Ethernet data packets and the layer-two switch can include a 100 mega-bits-per-second port for receiving the Fast Ethernet packets. The network switch can be a layer-two switch. The data packets stored in the packet buffers can be provided to the rate buffers prior to being formatted into radio frames. The data packets can be store in the packet buffers according to an amount of space available in the rate buffers. The data packets can be stored in the packet buffers in response to rain fade in the wireless link. The data packets can be stored in the packet buffers in response to interference in the wireless link. The data packets can be stored in the packet buffers in response to a detected bit error rate for communication via the wireless link.
In accordance with yet another aspect of the present invention, a terminal for a wireless link in a metropolitan area network includes an extender device for receiving data packets from a computer network coupled to the extender device and for forwarding the data packets; and a broadcast device coupled to the extender device, wherein the broadcast device includes: a network switch for receiving the data packets from the extender device; and a wireless transceiver coupled to the network switch for communicating the data packets over the wireless link. The terminal can also include a cable coupled between the extender device and the broadcast device wherein the cable comprises a twisted pair of conductors for providing the data packets from the extender device to the broadcast device. The twisted pair of conductors can be a Category 5 twisted pair of conductors. The broadcast device can also include a microwave antenna coupled to the wireless transceiver; and a housing coupled to the microwave antenna for enclosing the wireless transceiver. The network switch can include: a full-duplex 100BASE-T port for receiving a first portion of the data packets from the extender device; and a half-duplex 10BASE-T port for receiving a second portion of the data packets from the extender device. The terminal can include packet buffers coupled to the network switch wherein the terminal selectively stores data packets of the first portion in the packet buffers while simultaneously passing data packets of the second portion to the wireless transceiver. The network switch can be a layer-two switch. The layer-two switch can include a media independent interface (MII) coupled to the wireless transceiver.
In accordance with another aspect of the present invention, a method of communicating Fast Ethernet data packets over a wireless link includes steps of: receiving data packets into an extender device from a computer network coupled to the extender device; forwarding the data packets to a broadcast device coupled to the extender device, wherein the broadcast device includes a layer-two switch for receiving the data packets from the extender device and a wireless transceiver coupled to the layer-two switch for communicating the data packets over the wireless link; and communicating the data packets over the wireless link utilizing the wireless transceiver. The method can include a step of storing data packets received from the extender device by the layer-two switch into rate buffers coupled to the layer-two switch. The method can also include a steps of: removing data packets from the rate buffers; and formatting the data packets removed from the rate buffers according to radio frames. The data packets can be Fast Ethernet data packets and the layer-two switch can include a 100 mega-bits-per-second port for performing the step of receiving the Fast Ethernet packets. The method can also include a step of storing the data packets in packet buffers prior to storing the data packets in the rate buffers. The step of storing data packets in the packet buffers can be selectively performed in response to a level of space available in the rate buffers. The step of storing data packets in the packet buffers can be selectively performed in response to rain fade in the wireless link. The step of storing data packets in the packet buffers can be selectively performed in response to interference in the wireless link. The step of storing data packets in the packet buffers can be selectively performed in response to a detected bit error rate for communication via the wireless link.